By default 3rdRail opens in the Rails Perspective, as you can see by the window title
Rails - 3rdRail.
If for some reason you are not already using it, switch to the Rails Perspective.WindowOpen PerspectiveOther...Rails (default).

The New Rails Project Wizard opens:
The only thing you have to do is to name the project.
All relevant project defaults are set up for you.
A default database is set up, as is the WEBrick application server.
If you would like to change any of the defaults you can use the pulldown menus.
See dynamic help from within the wizard for more information.